Levers: 1st, 2nd, and 3rd Class Quiz

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Questions and Answers

What is a first class lever?

  • The fulcrum is at one end.
  • It has no mechanical advantage.
  • The load is between the fulcrum and the effort force.
  • The fulcrum is in the middle between the effort force and the resistance arm. (correct)

Define a lever.

A beam on a fulcrum that allows smaller force to move more weight.

Give examples of first class levers.

Scissors, can opener.

What is a second class lever?

<p>The load is between the fulcrum and the effort force.</p> Signup and view all the answers

Provide examples of second class levers.

<p>Nut cracker, wheelbarrow.</p> Signup and view all the answers

Calculate the mechanical advantage (MA) where LE=30 cm and LR=10 cm.

<p>MA=3</p> Signup and view all the answers

What is the mechanical advantage formula?

<p>MA= LE/LR</p> Signup and view all the answers

Describe a third class lever.

<p>Force is between the fulcrum and the load, with no mechanical advantage.</p> Signup and view all the answers

Give examples of third class levers.

<p>Bat, broom.</p> Signup and view all the answers

Calculate the mechanical advantage (MA) where LR=80 cm and LE=20 cm.

<p>MA=0.25</p> Signup and view all the answers

What is the formula for torque?

<p>T= F x L</p> Signup and view all the answers

Define torque.

<p>Moment of force, or rotational force.</p> Signup and view all the answers

What is the torque produced when a mechanic pulls on a 6-inch wrench with a force of 100 lbs?

<p>600 in-lb</p> Signup and view all the answers

What is the law of moments formula?

<p>ME= FE x LE</p> Signup and view all the answers

Calculate effort moments (ME) if the effort arm length (LE) is 153.5 in and the effort force (FE) is 63.5 lbs.

<p>ME= 9748.25 in-lbs</p> Signup and view all the answers

Determine the torque for a lever with a distance of 11.8 in and a force of 68.3 lbs-f.

<p>805.94 in-lb</p> Signup and view all the answers

What is a fulcrum?

<p>The fixed point around which a lever pivots.</p> Signup and view all the answers

What is the effort force?

<p>Effort arm.</p> Signup and view all the answers

What is the resistance force?

<p>Resistance arm.</p> Signup and view all the answers

If you change the _____, then the torque changes.

<p>distance</p> Signup and view all the answers

Flashcards

First-Class Lever

The fulcrum is positioned between the effort and resistance forces.

Lever

A beam that pivots on a fulcrum, enabling a smaller force to move a larger load.

Second-Class Lever

The resistance (load) is located between the fulcrum and the effort force.

Third-Class Lever

The effort force is positioned between the fulcrum and the resistance (load).

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Mechanical Advantage (MA)

Ratio of output force to input force, or effort arm length (LE) / resistance arm length (LR).

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Fulcrum

The fixed point on which a lever pivots.

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Effort Force

The force applied to a lever to move the load.

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Resistance Force

The force resisting the movement of a lever.

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Torque

The rotational force tending to cause rotation.

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Torque Formula

Force multiplied by the distance from the pivot point (Torque=F $ imes$ distance).

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Effort Arm

Distance from fulcrum to where effort is applied.

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Resistance Arm

Distance from fulcrum to where resistance or load is applied.

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Law of Moments

Effort moment = effort force × effort arm length

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Mechanical Advantage Calculation

Effort arm length (LE) divided by Resistance arm length (LR) (MA = LE/LR).

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Distance Effect on Torque

Changing the distance from the pivot point changes the torque.

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First-Class Lever Examples

Scissors, crowbars, pliers.

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Second-Class Lever Examples

Wheelbarrow, nutcrackers.

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Third-Class Lever Examples

Brooms, baseball bats, tweezers.

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Study Notes

Levers Overview

  • Levers consist of a beam resting on a fulcrum, allowing a smaller force to lift a larger weight.
  • There are three classes of levers, each defined by the position of the fulcrum, effort, and load.

First Class Lever

  • The fulcrum is positioned between the effort force and the resistance arm.
  • Examples include scissors and can openers.

Second Class Lever

  • The load is positioned between the fulcrum and the effort force.
  • Examples include nut crackers and wheelbarrows.
  • Mechanical Advantage (MA) can be calculated using the formula: MA = LE/LR, where LE = Load Effort, LR = Load Resistance.
  • Example problem: If LE = 30 cm and LR = 10 cm, MA = 3.

Third Class Lever

  • The effort force is located between the fulcrum and the load, resulting in no mechanical advantage.
  • Examples include bats and brooms.
  • Example problem: If LR = 80 cm and LE = 20 cm, MA = 20/80 = 0.25.

Torque

  • Defined as "Moment of Force," it refers to the rotational force applied around a pivot point.
  • Formula for torque: T = F x L, where T is torque (in-lbs), F is force (lbs-f), and L is distance (in).
  • Example problem: A mechanic pulling on a 6-inch wrench with a force of 100 lbs results in T = 6 * 100 = 600 in-lbs.

Law of Moments

  • The relationship is given by the formula: ME = FE x LE.
  • ME = Effort Moments (in-lbs), FE = Effort Force (lbs), LE = Effort Arm Length (in).
  • Example problem: For a first class lever with LE = 153.5 in and FE = 63.5 lbs, ME = 153.5 x 63.5.

Key Terms

  • Fulcrum: The fixed point around which a lever pivots.
  • Effort Force: The force applied to implement the lever's operation.
  • Resistance Force: The force that the lever is working against.
  • Changing the distance affects the torque generated by a lever.

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